NIEHS is leading a National Institutes of Health (NIH) long term study looking at the potential health effects of the oil spill in various responder populations. During FY 2013, the GuLF STUDY (Gulf Long-term Follow-Up Study) completed its baseline recruitment efforts. In total, the GuLF STUDY has completed 32,786 telephone interviews and 11,210 in-person visits where biospecimens are collected. Biospecimens are banked in a long-term storage facility using liquid nitrogen where appropriate. NIEHS investigators are actively conducting the follow-up interviews for the GuLF STUDY. Additionally, NIEHS investigators are working on designing and implementing the clinical visit for the Biomedical Surveillance Sub-cohort of the GuLF STUDY. Data collection is expected to begin in the winter of 2013. In the meantime, NIEHS investigators are working to obtain all of the available environmental and occupational exposure monitoring data in order to perform an accurate exposure assessment on the study population. Ongoing statistical modeling will lead to the development of cleanup-task exposure matrices that will allow assignment of exposure estimates for volatile compounds and other exposures related to oil spill cleanup. Approaches and preliminary results from exposure characterization efforts were presented at several international meetings.